It is generally known to provide an internal combustion engine including a pump assembly for pumping fluid through the engine, such as to operate a water pump to pump a cooling fluid through the engine to transfer heat from the engine. Pumps for incompressible fluids, such as oil and water, are often either gear pumps or vane pumps. In environments such as automotive engine systems, where are power take off (such as a belt pulley) is used to operate these pumps, the pumps will necessarily operate over a wide range of speeds, as the engine operating speed changes the pump changes speed resulting in changes in the output volume and the output pressure of the fluid exiting the pump.
In such devices, it is generally known to provide an electromagnetic clutch for selectively operating the pump. For example, one such device is disclosed in the international publication WO2010/148507 (A1), published Dec. 29, 2010, from international application number PCT/CA/2010/000978, filed Jun. 21, 2010, naming inventor Darrell F. Greene and commonly assigned with this application, then entire contents of which are incorporated herein by reference for all purposes. While the clutch of the '978 international application has particular applicability, there remains a need to continue to improve such devices. In particular, the clutch device and water pump combination of the international application include an undesirable and involved tolerance stack. Further, the axis of rotation of the hub (outer or external bearing) and the driven plate (inner or shaft bearing) is imperfect due to tolerances. This can cause the driven plate to orbit the hub rotation which can be perceived as the clutch “slipping” as the input and output speeds of rotation will be slightly different. Further, in the disclosed clutch device of the '978 international application, the press fit of the clutch pad on the shaft relative to the hub cannot insure the friction surfaces are perfectly parallel. This can result in uneven contact pressure on the friction plate and can lead to wear˜reduced capacity or slipping. Further, the assembly of the disclosed device of the '978 international application can be challenging since the position of the output clutch plate along the length of the shaft is significant in setting the gap of the input plate and electromagnet. If the gap is too large, the clutch device can experience lower performance when disengaging. Accordingly, it is desirable to improve the ease of assembly of the clutch device in manufacturing while maintaining a highly accurate and consistent tolerance gap in the electromagnetic components and clutch assembly.